Them wooden things in the ceilings

Chris · Feb 12, 2019

Hi,

I feel over the past few years more people are moving towards recessed downlights, on new builds its easier as you can mark out while there is no ceiling and know where they will land. But when retrofitting i have a hard time missing all the joists, are those stud finders any good? Or does anyone have any advice/tricks to help with them?

Thanks

Bobster · Feb 12, 2019

Tap with a hard object and you'll hear where the joists are.

ferg · Feb 12, 2019

A hammer to tap the ceiling.

I also use the magnets from my rod kit to find the nails or screws and consequently the bit of wood.

Gavin John Hyde · Feb 12, 2019

A 2 or 3mm drill bit is always useful. Find a joist and drill a hole. Maybe 3 small in all to find joist and its edges.
Building regs did(it may still do) give tables for 400, 450 and 600 mm spaced joists. And thickness of boards etc.
Measure out said gap and if its been built by a half sensible person you should find the next joist That gives you the spacing.
It will differ slightly around chimneys, stairs etc...
Most uk houses follow this spacing.
As above magnets can find the fixings. With a lot of older ceilings you can in right light see joists as the ceiling either side being slightly different.

Midwest · Feb 12, 2019

I use the above methods, and my trusty terminal bare blade terminal screwdriver, whose sole purpose is to find either side of joist. Then measure to next joist. It doesn’t locate noggins and metal pipes that might be in the way though.

I have a stud detector, and it’s of much use as a chocolate fire grate. I’ve heated the really expensive ones are ok.

littlespark · Feb 12, 2019

Never thought of using a magnet. Good idea.
Tapping and listening for a hollow is good but tricky in noisy environment or double thickness of plasterboard.

Modern builds are 400/ 450/ 600mm centres between joists, but the measurements never seem to land right.

Pete999 · Feb 12, 2019

Gavin John Hyde said:
A 2 or 3mm drill bit is always useful. Find a joist and drill a hole. Maybe 3 small in all to find joist and its edges.
Building regs did(it may still do) give tables for 400, 450 and 600 mm spaced joists. And thickness of boards etc.
Measure out said gap and if its been built by a half sensible person you should find the next joist That gives you the spacing.
It will differ slightly around chimneys, stairs etc...
Most uk houses follow this spacing.
As above magnets can find the fixings. With a lot of older ceilings you can in right light see joists as the ceiling either side being slightly different.

Get hold of the plans for the building, should show how the joists are laid out, within reason.

Wilko · Feb 12, 2019

I too use a small drill, "find first joist and measure" method. If this doesn't come up trumps, I go to the Man Himself for guidance.

[ElectriciansForums.net] Them wooden things in the ceilings

Bellendian · Feb 12, 2019

I always find that you either have to lift a strip of floorboards above, or remove a strip of plasterboard below, in order to drill joists and run cables through to new lights. So once you've done that you can see the joist spacings and drill for downlights accordingly.
Not sure how you guys are running the wires to 'join the dots' once youve drilled your downlight holes using the tap or magnet method?

Strima · Feb 12, 2019

I guess.

buzzlightyear · Feb 12, 2019

My proferd way of doing it with stud finder and a drill bit and then go for it ,if it looks like a golf course tuff.

richy3333 · Feb 12, 2019

I use one of those really strong magnets - rare earth? Else a small drill bit. I think the stud finders are next to useless

Midwest · Feb 12, 2019

Bellendian said:
I always find that you either have to lift a strip of floorboards above, or remove a strip of plasterboard below, in order to drill joists and run cables through to new lights. So once you've done that you can see the joist spacings and drill for downlights accordingly.
Not sure how you guys are running the wires to 'join the dots' once youve drilled your downlight holes using the tap or magnet method?

WiFi electrics, it’s the way to go. Ask Tesla.

MJPD29 · Feb 12, 2019

Pete999 said:
Get hold of the plans for the building, should show how the joists are laid out, within reason.

If only that were the case. Most shops I've worked in don't even have a plan of emergency lights or anything like it. It amazes me sometimes as soon as it's done they must just part company, I do a lot of work in the airport here and they don't have have a decent map of most areas!